Railway car suspension motion control system

ABSTRACT

A filled hydraulic system controls bounce, pitch and roll vibrational movements of a railroad car by controlling displacement of hydraulic fluid in and between double-acting single ended piston hydraulic cylinder units connected between the car body and at least one truck frame about the center bearing, there being check valves and a main pressure responsive spool valve in the system, as well as an accumulator and replenishing reservoir.

United States Patent 1191 Schultz RAILWAY CAR SUSPENSION MOTION CONTROL SYSTEM [75] Inventor: John C. Schultz, Buffalo, N.Y.

[73] Assignee: Houdaille Industries, Inc., Buffalo,

[22] Filed: Nov. 26, 1973 [21] Appl. No.: 419,107

[52] US. Cl 105/164, 105/199 A, 105/210 [51] Int. Cl. B61f 3/08, B6lf 5/24, B61f 5/50 [58] Field of Search 105/164, 199 A, 210

[56} References Cited UNITED STATES PATENTS 10/1971 Adler 105/164 X 2/1973 Law et a1. 105/164 1 Mar. 4, 1975 Primary Examiner-M. Henson Wood, Jr.

Assistant E.\'anzinerHoward Beltran Attorney, Agent, or Firml-lill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson {57] ABSTRACT A filled hydraulic system controls bounce, pitch and roll vibrational movements of a railroad car by controlling displacement of hydraulic fluid in and between double-acting single ended piston hydraulic cylinder units connected between the car body and at least one truck frame about the center bearing, there being check valves and a main pressure responsive spool valve in the system, as well as an accumulator and re plenishing reservoir,

22 Claims, 2 Drawing Figures RAILWAY CAR SUSPENSION MOTION CONTROL SYSTEM This invention relates to the control of motions of railroad cars related to their suspension systems, and is more particularly concerned with a new and improved hydraulic system for this purpose.

Pertinent elements involved in the suspension system of a railroad car are the car body, bolsters, suspension springs and truck assemblies. Basically, the car body is supported at its four corners by springs which rest on the truck frames, this being generally accomplished through a swivel plate connection between the car body and each bolster. This constitutes a mass elastic system. When track irregularities and force and speed disturb the elastic system at its natural frequency, large undesirable oscillations of the car body result. In running operation, a car body basically has three modes of vibration, that is, bounce wherein the entire car body vibrates vertically in phase, pitch" wherein the two ends vibrate vertically 180 out of phase, and roll wherein the vibrations are transverse to the length of the car and are l80 out of phase. Resonant disturbances which are sustained for any length of time result in a build-up of car body oscillation amplitudes to undesirable levels. Track surface irregularities which predominantly produce these disturbances are variations of the cross level of the tracks and rail joints. American railroads stagger the joints. Therefore, cars are subjected to disturbances which contribute to the roll mode.

conventionally, the railroad car body is supported through center plates on bolsters, carried on springs on the truck frames riding on the wheel and axle assembly. During major roll motion the weight of the car transfers to the side bearing on and between the car and bolster and the center plate separates. The suspension springs compress to virtually solid condition on the side toward which the roll extends and expand on the other side. The wheel opposite the roll direction lifts from the track. Permitting the roll to build sufficiently in magnitude may result in extremely high forces being imposed on the bolster and side frame requiring high endurance strength in these components. If wheel lift occurs while negotiating a curve or during a lateral disturbance, derailment may result.

On bad track, the roll problem occurs in a speed range of about to 30 miles per hour, requiring the engineer to take the train through this range as rapidly as possible or to slack off and pass through this speed range where track conditions are more desirable.

Vertical or bounce frequency is in the order of 2.5 cps and the roll frequency is in the order of 0.5 cps. Therefore, ordinary shock absorbers which will sufficiently damp the roll oscillations are much too stiff for normal vertical or bounce conditions.

An important object of the present invention is to overcome the foregoing and other disadvantages, deficiencies, inefficiencies, shortcomings and problems in railroad car suspension systems, and to attain important advantages and improvements and new and improved results through the system to be hereinafter described and which will satisfy the requirements for roll control as well as providing for efficient bounce and pitch control.

Another object of the present invention is to provide a new and improved railroad car suspension control system wherein all three basic modes of vibration are controlled in a simple, efficient and highly effective manner, wherein vibrations in the roll mode, especially, are effectively controlled.

A further object of the invention is to provide a new and improved filled hydraulic system for controlling railroad car suspensions, and involving an advantageous automatic, self-adjusting valve arrangement.

Still another object of the invention is to provide a new and improved control valve arrangement for rail-- road car suspension systems.

A still further object of the invention is to provide a new and improved vibration damping system for railroad cars utilizing single ended double acting hydraulic control cylinders.

Yet another object of the invention is to provide a new and improved vibration damping system for railroad cars.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

FIG. 1 is a schematic illustration of the manner in which bounce and pitch are controlled in a railroad car suspension, according to the present invention;

FIG. 2 illustrates roll control in the railroad car suspension, according to the present invention.

As shown in FIGS. 1 and 2, a typical railroad car as exemplified and which may be a passenger car but may. also be a freight car, includes a body 10 and a suspensison including a pair of trucks 11 (only one of which is shown) on each of which the body is mounted through the medium of swivel center plate means 12 on a bolster 13 extending transversely under the car. At each opposite end the bolster 13 is mounted on coil springs 14 supported by truck frame 15 carried by journals extending from the opposite ends of an axle 17 of flanged car wheels 18 riding on rails 19.

According to the present invention, a new and improved control system for damping bounce, pitch and roll is provided and which is mounted on and between the car body 10 and the suspension 11. Either or both of the trucks ll of the car may be equipped with the control system. For this purpose, at each side of the truck 11 a double-acting single ended hydraulic fluid displacement unit 20 is coupled to and between the body 10 and the truck frame 15 by suitable flexible joint means 21 such as universal joints to permit lateral and turning movements between the car body and the truck. In the present instance, the units 20 comprise rectilinear cylinder and piston assemblies each comprising a cylinder 22 having an upper end thereof coupled to the car body 10, and a piston rod 23 extending from the lower end of the cylinder coupled to the truck frame. If preferred, mounting of the hydraulic units 20 may be reversed, that is, the piston rod 23 in each instance attached to the carbody and the opposite end of the cylinder 22 attached to the truck frame 15. In this instance, the hydraulic units 22 are of the single ended type in which the piston rod 23 extends only.

through one end of the cylinder so that a piston 25 fixed on the piston rod and normally located intermediate the ends of the working chamber within the cylinder devides the working chamber within the cylinder into a subchamber 27 at the free end of the piston and.

a subchamber 28 on the opposite piston rod side of the piston. Any suitable means may be provided for filling the cylinders 22 with suitable oil.

Means providing hydraulic displacement connections between the units comprise a preferably flexible conduit or duct 31 communicating with the upper working subchamber 27 and a preferably flexible duct or conduit 32 communicating with the lower subchamber 28. First valve means are provided in the hydraulic displacement connections automatically responsive to hydraulic pressure in said connections as generated by said units for controlling displacement therethrough and thereby damping relative bounce and pitch motions between the car body and the suspension. Additional pressu r e sensit ive valve means are provided in the hydraiilic displacement connections inactive relative to bounce and pitch but operating automatically responsive to hydraulic pressure in said connections as generated by said units to damp roll motion between the car body and the suspension. These valve means are desirably housed within a housing which may be in the form of a block 33 with which the ducts 31 and 32 communicate.

In a desirable construction, as exemplified in FIG. 1, the valve means functioning to control and damp relative bounce and pitch motions comprise a set of check valves for the hydraulic circuit associated with each of the units 20. Such valves include a check valve 34 permitting relatively free hydraulic fluid displacement from the duct 31 to the duct 32 of each ofthe hydraulic units 20, and a check valve 35 which is normally biased as by means of a spring 37 for resisting hydraulic fluid displacement from the duct 32 to the duct 31 of each of the hydraulic units 20. Suitable means, (not shown) may be provided for adjusting the biasing thrust of the spring 37 in each instance.

Roll motion damping valve means comprise a reciprocatingly mounted spool valve member 38 mounted in a bore 39 and normally maintained centered therein by biasing means such as respective coiled compression springs 40 thrusting towards the respective opposite ends of the valve. Each of the ducts 32 communicates with a respective one end of the bore 39 through a branch 41 through the associated spring 41 with the adjacent end of the spool valve 38. Communication between the duct 32 in each instance with its companion duct 31 is provided for through a branch 42 of the duct 32 opening by way of a port 43 into the bore 39 spaced from the branch 41 and aligned with that side of an annular groove 44 of the spool valve 38 which is remote from the adjacent end of the spool valve, while a port 45 opens into the bore 39 in alignment with the opposite side of the groove 44 and has a branch passage 47 leading therefrom to a valve seat 48 for the biased check valve 35. A branch 49 from the duct branch 47 leads to a valve seat 50 for the check valve 34 with which the duct 31 communicates by way of a branch 51.

For pressure release and replenishing of oil, each of the ducts 31 communicates at its end remote from the cylinder 20 through a port 52 with a respective annular passage groove 53 in the spool valve 38 and adjacent to that side of the groove which is remote from the adjacent groove 44. Intermediate the sides of the grooves 52 a pressure relief or accumulator and replenishing reservoir 54 communicates by way of respective ducts 55 with the bore 39 for communication with the ducts 31. Hydraulic fluid filling means 56 may be provided for the reservoir 54.

In operating condition, the hydraulic system as described is self-contained and is filled with suitable hydraulic fluid such as oil, and vibration damping in the several modes of capability of the system. if effected automatically. For example, FIG. 1 demonstrates damping of bounce vibrations wherein the entire car body vibrates vertically in phase, and pitch vibrations wherein the two ends of the car vibrate vertically out of phase. The solid directional arrows represent hydraulic fluid displacement during compression wherein the distance between the car body 10 and the truck 11 reduces by yielding of the springs 14 as where the wheels 18 strike a raised rail joint. Although many prior suspension systems offer little damping for such vibra tional motions, the present system efficiently damps such motions. During the compression movement, the upper subchambers 27 of the hydraulic units 22 contract and the lower subchambers 28 expand. Hydraulic fluid from the upper chambers 27 displaces through the ducts 31 past the check valves 34 which are raised from their seats 50 as shown in full outline and the displaced fluid finds its way freely through the passages 49 bypassing the check valves 35 to the lower subchambers 28 through the ducts 32. Fluid displaced by the piston rods 23 is accepted by the reservoir 54 through the ports 52 the valve grooves 53 and the passageways 55. Any slight rolling movement is compensated for by stabilizing displacement between the ends of the ducts 31 through the ports 52, the grooves 53, the ducts 55 and the reservoir 54. Damping during rebound occurs by closing of the check valves 34, thereby compelling return flow as indicated by the dashed arrows in FIG. 1 through the biased check valves 35. As shown in dash outline in FIG. 1, each check valve 34 during rebound closes against its seat 50 and the check valves 35 are moved by the returning hydraulic fluid from their seats 48 against the bias of the springs 37 which thus restrict return flow to damp the rebound. Any fluid make up required by the chambers 27 is provided by the reservoir 54. During bounce and pitch damping, the spool valve 38 remains inactive, serving as a passive flow passage member in connecting the ducts 31 and 32 with one another and with the accumulator 54. Inasmuch as hydraulic pressures are substantially equal at each side of the hydraulic system during bounce and pitch vibrations, the valve 38 is held inactive even though the pressure exerted during rebound, especially, may be of fair magnitude.

During a roll movement as indicated by the directional arrow R in FIG. 2, the car body 10 tilts either to the left or to the right relative to the frame 15 of the truck 11, a rightward tilt being shown by way of example. In this condition, the lower subchamber 28 of the left-hand cylinder 22 and the upper subchamber 27 of the right-hand cylinder 22 will expel fluid and the opposite subchambers will expand. The tendency to expel fluid by the lower left-hand subchamber 28 will be resisted by the check valve 35 connected with the duct 32 from that subchamber and the flow from the upper right-hand subchamber 27 will displace through its duct 31 past the right-hand check valve 34 with little resistance. This provides a pressure differential from the left-hand circuit across the pressure sensitive spool valve 38 shifting it against the right-hand spring 40 toward the right as shown in FIG. 2. Fluid displaced by the right-hand piston rod 23 and from the right-hand circuit end of the spool valve 38 flows to the left-hand circuit through the ports 52 and the reservoir 54. Shifting of the spool valve 38 causes it to throttle the righthand port 52 while the left-hand port 52 remains open to its duct 31. Thereby, the reservoir 54 is cut off from the developing high pressure in the right-hand duct 31. At the same time, the movement of the valve 38 restricts and clamps movement of fluid through the righthand port 43 and the left-hand port 45 by progressively throttling them. This gradually increases resistance to the roll movement in a smooth manner as the car body tilt progresses to the point where right-hand tilt stop bearing 57 on the car body engages tilt stop bearing 58 on the bolster 13 and the corresponding tilt stop bearings at the left of the car increase their normal spaced relation and the center bearing plates 33 may partially separate. As the rolling motion reaches maximum, the bolster l3 tilts, compressing the springs 14 at the right side.

It will be understood, of course, that roll toward the left will be controlled in the same manner as control of roll to the right as has been described, since the control system is equal and complementary in each direction.

Not only viscous damping for vertical control, but also viscous damping for control of roll oscillations is provided by the present system. In roll oscillation damping, the oscillations will not be permitted to build up to undesirable amplitudes wherein wheel lift, derailment or high component loading might occur.

It will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.

I claim as my invention:

1. A system for controlling operational vibrations of a railroad car body relative to its suspension, comprisdouble-acting hydraulic fluid displacement units of the rectilinear piston and cylinder type wherein the piston rod extends from one end of the piston and the opposite end of the piston is free within the cylinder and having means for coupling the units to and between the respective opposite sides of the car body and suspension;

means providing hydraulic displacement connections between said units;

first valve means in said connections automatically responsive to hydraulic pressure in said connections as generated by said units for controlling displacement through the connections and thus damping relative bounce and pitch motions between the car body and the suspension;

additional pressure-sensitive valve means in said connections inactive relative to bounce and pitch but operating automatically responsive to hydraulic pressure in said connections as generated by said units to damp roll motion between the car body and suspension; and

accumulator means in said hydraulic displacement connections to accomodate piston rod displacement in said units.

2. A system according to claim 1, wherein each cylinder has means at one end for flexibly connecting it to one of said car body or suspension and the piston rod extends from the opposite end of the cylinder and includes means for flexibly connecting it to either the car body or the suspension alternatively to the cylinder.

3. A system according to claim 1, wherein said bydraulic unit cylinders have respective working subchambers, said hydraulic displacement connections comprising respective ducts communicating with said subchambers and with each other and with said accumulator means.

4. A system according to claim 3, wherein said first valve means comprise check valves operating to permit relatively free flow in one direction between the ducts which are companion to each of the hydraulic units and resist and damp flow in the opposite direction between the companion ducts.

5. A system according to claim 4, wherein said pressure-sensitive valve means comprise a reciprocable spool valve providing controllable passage means for displacement of fluid between said ducts and said accumulator means.

6. A system according to claim 5, including ports under the control of said spool valve and through which ports communication is effected between said ducts and said accumulator means.

7. A system according to claim 1, wherein said pressure-sensitive valve means comprise a spool valve and means normally biasing the spool valve into an inactive position, said spool valve providing passageways for generally free communication of said hydraulic connections therethrough with one another and with said accumulator means in the inactive position of the spool valve, said spool valve being responsive to roll motion displacement of hydraulic fluid from said units in opposition to said biasing means to throttle said passageways and thereby damp said roll motion.

8. A system according to claim 7, wherein said first valve means comprise check valves cooperating with said spool valve in effecting roll motion damping.

9. A system according to claim 1, wherein said bydraulic unit cylinders have respective working subchambers and said hydraulic displacement connections comprise respective ducts communicating with said subchambers, and pressure-sensitive valve means comprising a spool valve reciprocably mounted in a bore and having fluid displacement grooves therein, said respective ducts having ports communicating with said bore across said grooves, and said first valve means cooperating in said ducts with said spool valve operating in connection with said ports in effecting damping of roll motion between the car body and suspension.

10. A system according to claim 1, wherein said cylinders have the piston dividing the cylinder into upper and lower working subchambers, said connections comprising ducts leading from the upper subchamber and connected for normally generally free communication between one another and with said accumulator means said lower subchambers having ducts in commu nication therewith, passage means effecting communication between the upper subchamber ducts and the lower subchamber ducts, and said first valve means being in displacement controlling relation to said ducts in said passage means.

11. A system according to claim 10, wherein said pressure-sensitive valve means in part provide said passage means and control displacement between said upper subchamber ducts and also between said lower subchamber ducts and the upper subchamber ducts.

12. In combination with a railroad car having a body and suspension means comprising a truck having rail running wheels supporting a truck frame on which are mounted springs carrying a bolster on which the body is mounted, a system for controlling operational vibrations between the car body and the suspension, comprising:

double-acting hydraulic fluid displacement units of the recilinear piston and cylinder type wherein the piston rod extends from one end of the piston and the opposite end of the piston is free within the cylinder and having means coupling the units at respectively opposite sides of the truck to the truck frame and to the car body;

means providing hydraulic displacement connections between said units;

first valve means in said connections automatically responsive to hydraulic pressure in said connections as generated by said units for controlling displacement through the connections and thus damping relative bounce and pitch motions between the car body and the suspension;

additional pressure-sensitive valve means in said connections inactive relative to bounce and pitch, but operating automatically responsive to hydraulic pressure in said connections as generated by said units to damp roll motion between the car body and suspension; and

accumulator means in said hydraulic dsiplacement connections to'accommodate piston rod displacement in said units.

13. A combination according to claim 12, wherein each cylinder has means at one end for flexibly coupling it to one of said car body or truck frame and the piston rod extends from the opposite end of the cylinder and includes means for flexibly connecting it to either the car body or the truck frame alternatively to the cylinder.

14. A combination according to claim 12, wherein said hydraulic unit cylinders have respective working subchambers, said hydraulic displacement connections comprising respective ducts communicating with said subchambers, the ducts connecting one of the chambers of the units being normally in free communication with one another through said accumulator means, and the ducts communicating with others of the subchambers having communication with the freely communicating ducts through said valve means.

15. A combination according to claim 14, wherein said first valve means comprise check valves operating to permit relatively free flow in one direction between the ducts which are companion to each of the hydraulic units and resist and dampflow in the opposite direction between the companion ducts.

16. A combination according to claim 15, wherein said pressure-sensitive valve means comprises a reciprocable spool valve providing controllable passage means for displacement of fluid between said ducts.

17. A combination according to claim 16, including ports under the control of said spool valve and through which ports communication is effected between said ducts and said accumulator means.

18. A combination according to claim 12, wherein said pressure-sensitive valve means comprise a spool valve and means normally biasing the spool valve into an inactive position, said spool valve providing passageways for generally free communication of said hydraulic connections therethrough with one another and with said accumulator means in the inactive position of the spool valve, said spool valve being responsive to roll motion displacement of hydraulic fluid from said units in opposition to said biasing means to throttle said passageways and thereby damp said roll motion.

19. A combination according to claim 18, wherein said first valve means comprise check valves cooperating with said spool valve in effecting roll motion damping.

20. A combination according to claim 12, wherein hydraulic cylinders have respective working subchambers and said hydraulic displacement connections comprise respective ducts communicating with said subchambers, said pressure-sensitive valve means comprising a spool valve reciprocably mounted in a bore and having fluid displacement grooves therein, said respective ducts having ports communicating with said bore across said grooves, and said first valve means cooperating in said ducts with said spool valve operating in connection with said ports in effecting damping of roll motion between the car body and suspension.

21. A combination according to claim 12, wherein each cylinder has the piston dividing the cylinder into upper and lower working subchambers, said connections comprising ducts leading from the upper subchamber and connected for normally generally free communication with one another and with said accumulator means, said lower subchambers having ducts in communication therewith, and passage means effecting communication between the upper subchamber ducts and the lower subchamber ducts, and said first valve means being in displacement controlling relation to said ducts in said passage means.

22. A combination according to claim 21, wherein said pressure-sensitive valve means in part provide said passage means and control displacement between said upper subchamber ducts and also between said lower subchamber ducts and the upper subchamber ducts. 

1. A system for controlling operational vibrations of a railroad car body relative to its suspension, comprising: double-acting hydraulic fluid displacement units of the rectilinear piston and cylinder type wherein the piston rod extends from one end of the piston and the opposite end of the piston is free within the cylinder and having means for coupling the units to and between the respective opposite sides of the car body and suspension; means providing hydraulic displacement connections between said units; first valve means in said connections automatically responsive to hydraulic pressure in said connections as generated by said units for controlling displacement through the connections and thus damping relative bounce and pitch motions between the car body and the suspension; additional pressure-sensitive valve means in said connections inactive relative to bounce and pitch but operating automatically responsive to hydraulic pressure in said connections as generated by said units to damp roll motion between the car body and suspension; and accumulator means in said hydraulic displacement connections to accomodate piston rod displacement in said units.
 2. A system according to claim 1, wherein each cylinder has means at one end for flexibly connecting it to one of said car body or suspension and the piston rod extends from the opposite end of the cylinder and includes means for flexibly connecting it to either the car body or the suspension alternatively to the cylinder.
 3. A system according to claim 1, wherein said hydraulic unit cylinders have respective working subchambers, said hydraulic displacement connections comprising respective ducts communicating with said subchambers and with each other and with said accumulator means.
 4. A system according to claim 3, wherein said first valve means comprise check valves operating to permit relatively free flow in one direction between the ducts which are companion to each of the hydraulic units and resist and damp flow in the opposite direction between the companion ducts.
 5. A system according to claim 4, wherein said pressure-sensitive valve means comprise a reciprocable spool valve providing controllable passage means for displacement of fluid between said ducts and said accumulator means.
 6. A system according to claim 5, including ports under the control of said spool valve and through which ports communication is effected between said ducts and said accumulator means.
 7. A system according to claim 1, wherein said pressure-sensitive valve means comprise a spool valve and means normally biasing the spool valve into an inactive position, said spool valve providing passageways for generally free communication of said hydraulic connections therethrough with one another and with said accumulator means in the inactive position of the spool valve, said spool valve being responsive to roll motion displacement of hydraulic fluid from said units in opposition to said biasing means to throttle said passageways and thereby damp said roll motion.
 8. A system according to claim 7, wherein said first valve means comprise check valves cooperating with said spool valve in effecting roll motion damping.
 9. A system according to claim 1, wherein said hydraulic unit cylinders have respective working subchambers aNd said hydraulic displacement connections comprise respective ducts communicating with said subchambers, and pressure-sensitive valve means comprising a spool valve reciprocably mounted in a bore and having fluid displacement grooves therein, said respective ducts having ports communicating with said bore across said grooves, and said first valve means cooperating in said ducts with said spool valve operating in connection with said ports in effecting damping of roll motion between the car body and suspension.
 10. A system according to claim 1, wherein said cylinders have the piston dividing the cylinder into upper and lower working subchambers, said connections comprising ducts leading from the upper subchamber and connected for normally generally free communication between one another and with said accumulator means said lower subchambers having ducts in communication therewith, passage means effecting communication between the upper subchamber ducts and the lower subchamber ducts, and said first valve means being in displacement controlling relation to said ducts in said passage means.
 11. A system according to claim 10, wherein said pressure-sensitive valve means in part provide said passage means and control displacement between said upper subchamber ducts and also between said lower subchamber ducts and the upper subchamber ducts.
 12. In combination with a railroad car having a body and suspension means comprising a truck having rail running wheels supporting a truck frame on which are mounted springs carrying a bolster on which the body is mounted, a system for controlling operational vibrations between the car body and the suspension, comprising: double-acting hydraulic fluid displacement units of the recilinear piston and cylinder type wherein the piston rod extends from one end of the piston and the opposite end of the piston is free within the cylinder and having means coupling the units at respectively opposite sides of the truck to the truck frame and to the car body; means providing hydraulic displacement connections between said units; first valve means in said connections automatically responsive to hydraulic pressure in said connections as generated by said units for controlling displacement through the connections and thus damping relative bounce and pitch motions between the car body and the suspension; additional pressure-sensitive valve means in said connections inactive relative to bounce and pitch, but operating automatically responsive to hydraulic pressure in said connections as generated by said units to damp roll motion between the car body and suspension; and accumulator means in said hydraulic dsiplacement connections to accommodate piston rod displacement in said units.
 13. A combination according to claim 12, wherein each cylinder has means at one end for flexibly coupling it to one of said car body or truck frame and the piston rod extends from the opposite end of the cylinder and includes means for flexibly connecting it to either the car body or the truck frame alternatively to the cylinder.
 14. A combination according to claim 12, wherein said hydraulic unit cylinders have respective working subchambers, said hydraulic displacement connections comprising respective ducts communicating with said subchambers, the ducts connecting one of the chambers of the units being normally in free communication with one another through said accumulator means, and the ducts communicating with others of the subchambers having communication with the freely communicating ducts through said valve means.
 15. A combination according to claim 14, wherein said first valve means comprise check valves operating to permit relatively free flow in one direction between the ducts which are companion to each of the hydraulic units and resist and damp flow in the opposite direction between the companion ducts.
 16. A combination according to claim 15, wherein said pressure-sensitive valve means comprises a reciprocable spool valve prOviding controllable passage means for displacement of fluid between said ducts.
 17. A combination according to claim 16, including ports under the control of said spool valve and through which ports communication is effected between said ducts and said accumulator means.
 18. A combination according to claim 12, wherein said pressure-sensitive valve means comprise a spool valve and means normally biasing the spool valve into an inactive position, said spool valve providing passageways for generally free communication of said hydraulic connections therethrough with one another and with said accumulator means in the inactive position of the spool valve, said spool valve being responsive to roll motion displacement of hydraulic fluid from said units in opposition to said biasing means to throttle said passageways and thereby damp said roll motion.
 19. A combination according to claim 18, wherein said first valve means comprise check valves cooperating with said spool valve in effecting roll motion damping.
 20. A combination according to claim 12, wherein hydraulic cylinders have respective working subchambers and said hydraulic displacement connections comprise respective ducts communicating with said subchambers, said pressure-sensitive valve means comprising a spool valve reciprocably mounted in a bore and having fluid displacement grooves therein, said respective ducts having ports communicating with said bore across said grooves, and said first valve means cooperating in said ducts with said spool valve operating in connection with said ports in effecting damping of roll motion between the car body and suspension.
 21. A combination according to claim 12, wherein each cylinder has the piston dividing the cylinder into upper and lower working subchambers, said connections comprising ducts leading from the upper subchamber and connected for normally generally free communication with one another and with said accumulator means, said lower subchambers having ducts in communication therewith, and passage means effecting communication between the upper subchamber ducts and the lower subchamber ducts, and said first valve means being in displacement controlling relation to said ducts in said passage means.
 22. A combination according to claim 21, wherein said pressure-sensitive valve means in part provide said passage means and control displacement between said upper subchamber ducts and also between said lower subchamber ducts and the upper subchamber ducts. 